The genus Yersinia contains three pathogenic species. Y. enterocolitica and Y. pseudotuberculosis are enteric pathogens that cause gastroenteritis, and Y. pestis is the causative agent of plague. The Yersinia RovA protein is a member of the MarR/SlyA family of bacterial global regulators and was first identified as a positive regulator of inv, the gene that encodes invasin, a critical virulence factor involved in the initial stages of infection. RovA is necessary for full virulence and a rovA mutant is more attenuated than an inv mutant, which indicates that RovA may regulate other genes required for virulence. The regulation of multiple virulence factors by RovA provides a central control point to mediate virulence and a regulatory checkpoint to control expression of several genes. Therefore, environmental factors that induce or repress expression of rovA will in turn regulate several genes at once, allowing for the coordination of expression of factors necessary to establish infection. Here I propose to identify the expression pattern of rovA during infection and to determine the environmental factors that regulate rovA expression. Furthermore, rovA regulators will be identified using transposon mutagenesis and promoter binding assays. Finally, I propose to determine whether rovA regulators interact with the rovA promoter and the role of rovA regulators in virulence. Completion of these aims will greatly enhance our knowledge of the regulation of an important virulence factor in Y. enterocolitica and may identify novel virulence regulatory pathways in Yersinia.